The present invention relates to a method for manufacture of multilayer wiring boards and to the resulting multilayer wiring boards, and more particularly to a method for manufacture of multilayer wiring boards comprising a substrate and a wiring pattern, a resistor film pattern or an insulator film pattern formed on the substrate by laminating two or more layers of different materials and to the resulting multilayer wiring boards.
In general, as multilayer wiring boards on which electronic components are to be mounted in high density, there are used multilayer wiring boards prepared by forming a thin film multilayer wiring comprising an organic insulating film and a metal wiring pattern on a substrate. In the multilayer wiring boards of this type, a main conductor layer (metal wiring pattern) and an antioxidation protective layer are successively formed to prevent oxidation of the surface of the metal wiring pattern. Therefore, the wiring pattern has a multiple structure comprising the conductor layer and the antioxidation protective layer which are laminated. Furthermore, in such multilayer wiring boards, for the purpose of flattening of the boards the insulating layer is constructed of a plurality of different insulating films in a laminated form.
Hitherto, processing of wiring materials and insulating films of such a multilayer structure has been carried out by etching the respective laminated layers successively or the two or more layers simultaneously from the upper layer side in accordance with photoetching or the like to form a pattern. Alternatively, the pattern can be formed by repeating the photoetching by the number of times corresponding to the number of the wiring materials, the resistor materials and the insulating materials.
A prior art on the multilayer wiring boards of this type is disclosed, for example, in JP 60-10755A.
In the technique of the prior art above, when the wiring materials, resistor materials and insulating materials of multilayer structure are subjected to etching, the etching is carried out successively in the order of from the top layer to the lower layers and, therefore, the under-etching of the upper layers occurs when the lower layer is etched. When a film of a wiring material is further formed over the formed wiring pattern of a multilayer structure, the film of the wiring material cannot be sufficiently formed at the under-etched portion to cause decrease of coverage. Moreover, in order to prevent occurrence of the under-etching in the prior technique, a plurality of patterning steps of a mask material are needed and a plurality of photoetching steps are needed. Thus, the number of processing steps increases undesirably.